Typex timelines

If you don’t know the history of the Typex cipher machine read here.

Something that most authors don’t mention is that the 1943-5 Typex was different from the 1939 version.Initially the machine had only 5 rotors.As such it’s security was higher than a commercial Enigma but compared to the Enigma I used by the German Armed Forces it was inferior.

The Brits however were true professionals and they upgraded the Typex with plugboard (in reality a rewirable reflector) ,many sets of rotors and reversible inserts ( ‘’split’’ rotors ).These modifications made the Typex much more secure than the Enigma I.

From files  HW 40/89 , ADM 1/27186  in the British Archives I got the following information :

Timeline :

9/39 : 5 solid drums only

1/7/40 : Red drums introduced

Early 1941 : Plugboard started being introduced on certain links

Nov-Dec ’42 : reversible inserts introduced

May ’44 : Inter-Service plugboard key

Oct ’44 : 3 new inter-service drums introduced ( 7 originally )

Naval Typex : 

5 drums ‘’Black’’ used initially

2 drums ‘’Red’’ introduced 1^st June ‘41

7 cypher drums - distributed  late ’42 early ’43 , used from 1^st Feb ‘43

7 code drums -  distributed  late ’42 early ’43 , used from 1^st April ‘43

Plugboard – from Nov’41 started to be fitted to machines , 1^st March ’42 Naval plugboard settings key introduced , by late ’43 bulk of Naval Cypher X traffic enciphered using plugboard keys – at the time Naval Code X not using plugboard ,

Traffic -   by July ’42 Typex carried 1/3 of Naval traffic  , by end ’43 50% Typex-50% book systems , by Dec ’44 55% Typex-45% book systems

Mechanical problems encountered ( failure of the drums to rotate , rotation at incorrect intervals )